1. Field of the Invention
The invention relates to pipes and tubular conduits; and, more particularly, to a conduit having a constant volume flow despite varying inlet pressure, the constant volume being variable.
2. Description of the Prior Art
In U.S. Pat. No. 3,763,884 to Grassi et al, a constant volume flow device is described which accurately provides a constant fluid flow. In this device, fluid pressure acts on a spring-biased restricting member which reduces the cross-sectional area of the passage through which air flows and maintains a constant volume air flow. The device of the Grassi et al patent has a particular relationship between the areas of the restricting member, the spring force and the shape of the fluid passage to automatically provide constant fluid flow regardless of variations in the inlet pressure.
However, the supply of air to such devices varies. The aforementioned patent to Grassi et al has limited field of adjustment of approximately fifteen percent (15%). That is, the device described in the Grassi et al patent can handle an increase in air flow of approximately fifteen percent (15%) before the spring therein goes beyond its elastic limit.
There is thus a need for a constant volume flow device wherein the value of the constant volume setting of the device may be varied to accommodate a varying supply of air thereto.